This invention relates generally to an apparatus for joining sheets of material and specifically to a die assembly and retainer used therein.
It is old in the art to join multiple pieces of sheet metal by punching or otherwise manipulating them to cause these sheets to be deformed into an interlocking relationship in a localized area. However, such joints have traditionally required the shearing of the sheet material and hence are not suitable for leak proof applications unless a sealant is applied. The formation of such joints is also frequently destructive of the corrosion resistance of coated materials. In addition, the known apparatuses for forming the joints are frequently complex in design. This complexity increases the cost of the equipment, as well as the energy required for operation.
More recently, the inventor of the present invention has developed an apparatus for producing more cost effective and aesthetically pleasing leak proof and lanced joints. These are known within the industry as Tog- L-Loc.RTM. and Lance-N-Loc.RTM. joints which can be obtained from the assignee of the present invention. These improved joints are disclosed within U.S. Pat. No. 5,150,513 which issued on Sep. 29, 1992 and U.S. Pat. No. 5,177,861 which issued on Jan. 12, 1993, both of which are incorporated by reference herein.
Moreover, the use of coiled springs to inwardly retain a plurality of movable die pieces against an anvil for joining sheets of material is shown in Japanese patents 148036 entitled "Joining Device For Thin Metallic Plate" and 148039 entitled "Joining Device For Metallic Sheet." However, in both of these devices, the coiled spring is not canted. Furthermore, an outer sleeve is not shown surrounding the spring and movable die pieces.
In accordance with the present invention, the preferred embodiment of a new and useful apparatus for joining sheets of material employs a die assembly having an anvil peripherally bordered by a plurality of movable die segments and a spring which urges the die segments radially toward the anvil. In a further aspect of the present invention, the spring is a coiled and canted spring. In another aspect of the present invention, the spring secures the die segments within an outer sleeve. In yet another aspect of the present invention, a unique die retainer has provisions for retaining a die assembly and for fastening such to a work surface.
The apparatus of the present invention is advantageous over conventional devices in that a plurality of die segments and a spring can be assembled to an anvil in a more cost effective, reliable and more durable manner. Furthermore, the spring and die segment construction of the present invention allows for quicker and easier disassembly and is self cleaning of undesirable foreign matter. Moreover, a spring serves to reliably retain a plurality of die segments within an outer sleeve regardless of the attitude of the die assembly. A canted spring of the present invention also allows a die assembly to be more compact in a radial direction as compared to prior uncanted spring devices. Furthermore, an outer casing substantially surrounds a plurality of die segments and a spring thereby protecting the die segments and spring from foreign matter and from inadvertent abuse. The specific mounting construction of die retainers of the present invention are also advantageous over traditional devices since the present invention provides for a secure yet easily removable die retainer which can be fastened to a variety of work surfaces. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.